Various designs exist to introduce shock absorbing elements into athletic shoes. For example, Giese et al., U.S. Pat. No. 4,316,332, discloses an athletic shoe construction having shock absorbing elements in the heel and forefoot areas of the sole portion of the shoe. These elements are surrounded on their sides by comparatively hard rim portions of a sole shell or midsole. Also, Stirtz et al., U.S. Pat. No. 4,297,796, discloses a shock-absorbing system for athletic shoes, the shoes having a foot-cushioning inner sole member to one face in which, and to at least a portion of the rim in which, is bonded an open mesh web. The interwoven strands of the web act as force-transmitters with respect to the sole member, and cause a localized foot-produced deformation in the member to be distributed to other regions in the member.
The applicant has devised a novel system to increase the performance of athletic shoes by introducing elements into the soles of athletic shoes that provide excellent shock attenuation and kinetic energy returning properties. The kinetic energy returning property refers to the ability of a material to quickly return to its original shape after deformation, the deformation resulting from the effect of kinetic energy received from another source. For example, rubber balls have excellent kinetic energy returning properties as evidenced by their immediate and sharp bounce when thrown against a surface. Athletic shoes having such shock attenuation and kinetic energy returning properties are desirable because shock attenuation reduces the possibility of injury to the wearer and a kinetic energy returning property imparts a "springiness" quality to the shoes.
The present invention achieves the desired objectives by a coupled two module unit that is inserted into a cavity located in the heel portion of the midsole. One module component of the unit is a rubber containing material, this module being much softer than the other module of the unit.
The present invention comprising certain novel features and a combination of parts is hereinafter fully described and illustrated in the accompanying drawings and is particulary pointed out in the appended claims. It is understood that various changes in the particulars may be made without departing from the spirit of substance of the present invention.